The sensory epithelium of the inner ear is composed of one row of inner hair cells and three rows of outer hair cells, located within the organ of Corti that resides on the basilar membrane. In the intact ear, sound pressure waves from the environment travel through the external auditory canal, are then transmitted through the ear drum and middle ear ossicles to the fluid within the cochlea. The fluid movement within the cochlea induces the depolarization of the sensory epithelium formed by the hair cells. This depolarisation is transformed into nervous signals which are transmitted from the base of the hair cells to the dendrites of the spiral ganglion, which is the first neuron on the auditory pathway and from the spiral ganglion further to the central auditory system, and finally reaching the auditory cortex to elicit a sound perception. Further, it is known that auditory nerve fibres are frequency tuned so that the ones from the base of the cochlea transmit high frequency sound information and the ones from the apical turn are transmit information of low frequency tones to the brain. The nervous signals transmitted via the spiral ganglion cells to the central auditory system can be recorded as auditory brainstem responses (ABR).